Method for continuously manufacturing a communication cable

ABSTRACT

A method and an apparatus therefor of manufacturing a communication cable, comprising a primary stage in which a plurality of insulated conductors are wound on each of a plurality of identical winding reels and a secondary stage in which the winding reels are now used as feeding and twisting reels and in which the conductors wound on each of the feeding and twisting reels are twisted into a strand and a plurality of the thus formed strands are further twisted into a stranded cable which is thereafter coated with a protective sheath. The three major steps of the secondary stage are carried out all continuously.

Unlted States Patent 1 1 [111 3,722,203 Akachi 14 1 Mar. 27, 1973 [5 METHOD FOR CONTINUOUSLY 2,904,846 9/1959 Smith ..57 35 MANUFACTURING A 2,572,052 10/1951 Pheazey ..57/3 COMNIUNICATION CABLE 2,981,049 4/1961 Crosby et a1. ....57/34 AT 2,998,692 9/1961 Garner ..57 3 Inventor: a e u v KanagaWa-ken, 3,187,495 6/1965 Christian, Jr.... ..57/34 AT I Japan 3,538,697 1 H1970 Homor et al ..57/34 AT [73] Assignee: Oki Densen Kabushiki Kaisha,

Kanagawa ken, Japan; a part Primary ExammerWerner H. Schroeder terest Attorney Kelman and Berman [22] Filed: Oct. 29, 1970 [57] ABSTRACT [21] Appl' 85212 A method and an apparatus therefor of manufacturing a communication cable, comprising a primary stage in [30] Foreign Application Priority Data which a plurality of insulated conductors are wound Nov 1 5 1969 Ja an 44/91494 on each of a plurality of identical winding reels and a a p c da y Stage in which the d g reels are now 52 US. Cl. .57/160, 57/34 AT 57/63 used as feeding and twisting reels and in Whih the 57 /94 conductors wound on each of the feeding and twisting 51 Im. c1. ..H01b 13/04 reels are twisted into a Strand and a plurality of the [58] Field of Search ..57/3, 7, 13, 15, 16, 17, 18, thus formed Strands are further twisted into a Stranded 57/34 R, 34 AT, 35, 62, 63, 64, 156, 162, cable which is thereafter coated with a protective 164 sheath. The three major steps of the secondary stage are carried out all continuously. [56] References Cited UNITED STATES PATENTS 4 Claims, 2 Drawing Figures 3,412,544 11/1968 Sugi et al ..57/34 AT METHOD FOR CONTINUOUSLY MANUFACTURING A COMMUNICATION CABLE The present invention relates to a method for manufacturing a communication cable and an apparatus for carrying out the method.

The process of manufacturing a communication cable usually includes the steps of producing insulated conductors, twisting the insulated conductors into strands of component conductors, further twisting or cabling the strands into a stranded cable and covering the resultant cable with a protective sheath. Each of 7 these steps has been sped up remarkably supported by the recent advance in the related technology. In the most advanced cable manufacturing technique which is presently put into practice, the production rate of the plastic insulated conductors has reached about 1,000 to 1,500 meters per minute. The strands of the component conductors, on the other hand, can now be produced at the rate of about 2,000 to 2,400 pitches per minute and the thus formed strands can be twisted into a stranded cable at the rate of 50 to 70 meters per minute. The rate of covering the cable with a protective sheath has increased to about 50 to 70 meters per minute. Various attempts are still made in the industry in quest of further simplified and more efficient production schemes in the individual steps of communication cable production. One example of such attempts is an improvement in the structure of the communication cable and another example is a process in which the individual steps proceed concurrently, viz., in continuous steps. More specifically, a practice has been proposed in which the steps of stretching component conductors and extruding a plastic material to cover the component conductors are combined into continuous steps. Another successful practice is the one in which the steps of twisting the strands of component conductors into a cable and covering the cable with a protective sheath are combined into continuous steps, whichpractice is disclosed in the applicant's US. Pat. No. 3,446,001 which is concerned with a method and apparatus for twisting strands of component conductors at an increased speed.

The rate of twisting the insulated conductors has been sped up more than 10 times in the last years, to about 200 to 240 meters per minute assuming that each of the twisting pitches is 100 millimeters. Even such a high rate of production of the strands of component conductors is not fully satisfactory to meet the ever increasing demands for industrial communication cable. The limitation in the speed-up of producing strands of component conductors is now one of the most serious problems in the communication cable production industry.

It may be felt that the cabling and sheathing rates, which are about 50 to 70 meters per minute as previously noted, are not very high as compared with the rates of other cable production steps. The fact is, however, that these cabling and sheathing rates are high enough to be fully acceptable because, if the cable is made up of two hundred paired strands, 20,000 to 28,000 meters of conductor are processed per minute.

The conductors are usually insulated on a plastic extruding machine at a rate of about l,000 to 1,500 meters per minute as previously discussed. When two conductors are insulated simultaneously, the production rate amounts to about 700 to 1,000 meters per minute because the problems encountered in the production of a singleinsulated conductor are alleviated where two insulated conductors are produced in a single machine so that the production rate is increased about 30 to 40 per cent. Such problems include (1) the limited rates of feeding and winding the conductor due to' the intrinsic features of the feeding and winding devices, (2) the increased pressure in the extrusion head applying an excess force to the conductor, (3) the tendency of the conductor to be stretched by the resistance of the water in a cooling bath through which the conductor is passed and (4) the development of a back pressure around the extruding screw due to the increase in the pressure in the extrusion head, reducing'efficiency.

If it is desired to twist the insulated conductors at a rate in agreement with the production of two insulated conductors in a single machine, the conductors must be twisted at about 10,000 to 14,000 pitches per minute if an elementary pitch is about millimeters. Such a high rate of twisting is not available in twisting apparatus commonly in use. If, on the contrary, the rate of production of two insulated conductors in a single step is reduced so as to be compatible with the available rate of twisting the conductors which is about 2,000 to 2,400 pitches per minute, the extruder could not be utilized to its full capacity.

A proposal has been made by the applicant to have the component conductors twisted at pitches varying stepwise, the proposal being disclosed in the applicants US. patent application Ser. No. 78,870, filed on Oct. 7, 1970. As disclosed in the copending application, several conductors are passed from one or more feeding reels through an apertured element rotating at a first speed in which they are twisted about each other, the resulting strand is wound on a take-up reel rotating at a second speed about the axis of rotation of the afore-mentioned apertured element, the axis extending in the direction in which the conductors are fed to the apertured element at a third speed. In operating this device, one of the three speeds is held constant, and one of the other two speeds may then be controlled in such amanner that the pitch in the ultimate strand varies stepwise along the length thereof. This pitch variation apparently results from the variation in the overall diameter of the coil of conductors on the feeding reel or reels or the variation in the diameter of the coil formed on the take-up reel as the process continuesBy virtue of this improvement, the rate of twisting the conductors has been raised to about 5,000 pitches per minute. The step of twisting the conductors in the method disclosed therein may be successfully combined with the step of extruding three or four insulated conductors at a time. Where, however, two insulated conductors are to be extruded simultaneously, the rate of twisting the conductors can not be in agreement with the rate at which the insulated conductors are produced. If the rates of producing and twisting the two insulated conductors must be compatible, the sizes of the feeding and winding reels must be reduced significantly, sacrificing efficiency in cabling or twisting the resultant strands in the succeeding step.

The steps of twisting the insulated conductors and the resultant strands may be combined into continuous steps. The rate at which the strands of component conductors are twisted into a stranded cable, as presently available, is of the order of about 50m 70 meters per minute as previously noted. If, therefore, each of the pitches of twisting is 70 mm, it is enough that the component conductors be stranded at about 700 to 1,000

pitches per minute. This means that the rate of twisting the component conductors into strands is compatible with the available rate of twisting the resultant strands in a step succeeding to the conductor twisting step. An apparatus adapted to produce the strands and the stranded cable in continuous operation in two steps at this rate would be of compact and simplified construction. The only problem is that as many conductor twisting machines must be used as there are strand. Where hundreds of strands are to be twisted into a cable, hundreds of twisting machines would be needed, critically adding to the cost of equipment as a-whole. This will more than offset the simplified construction of the entire apparatus.

An important object of the present invention is therefore to provide a method for manufacturing a communication cable at an increased production rate and in a simplified process.

Another important object is to provide a method which is adapted to produce a communication cable less costly with use of simplified production equipment requiring a minimum of floor space in a factory.

Still another important object is to provide a method for manufacturing a communication cable in continuous steps which are so streamlined as to dispense with the conveyance of any material throughout the various cable manufacturing operations.

Still another important object is to provide an apparatus which is adapted to carry out the method proposed by the present invention.

In order to achieve these and other objects, the present invention proposes to manufacture a communication cable in two consecutive stages. In the primary stage, bare conductors are withdrawn from feeding reels and are covered with an insulating material. The insulated conductors are then wound on a plurality of winding reels. In this instance, the same number of insulated conductors are wound in the same length on each of the winding reels. The winding reels on which the insulated conductors are wound are utilized as feeding reels in the succeeding secondary stage. In the secondary stage, the insulated conductors are unwound and twisted into strands of component conductors. The strands are thus produced from respective, secondary feeding reels and are thereafter twisted or stranded into a cable. The cable is then covered with a protective sheath. The feeding and twisting of the insulated conductors, the further twisting of the resultant strands, and the covering of the cable with the protective sheath are all performed in continuous steps in a single production line. The rates at which the component insulated conductors are fed and twisted into the strands and the rates at which the strands are twisted into the cable are synchronized.

The objects, features and advantages of the method and apparatus according to the present invention will become more apparent from the following description of the invention taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a schematic view showing the primary stage of the method and apparatus according to the present invention; and

FIG. 2 is a schematic view showing a preferred embodiment of the secondary stage of the method and apparatus according to the present invention.

Thev term strand as herein used as a noun is intended to designate a bunch of twisted insulated conductors and to include quads and pairs as is customary in the art.

Referring now to FIG. 1, there is illustrated the primary stage of the arrangement for manufacturing a communication cable in accordance with the present.

invention. Two feeding reels 10 and 10' have mounted thereon coils 11 and 11' of bare conductors 12 and 12', respectively. The coils 11,11 may preferably be substantially identical in the initial outside diameters. The conductors 12 and 12' are unwound from the respective feeding reels 10 and 10 as the reels are rotated and are passed through apertured discs 13 and 13', respectively. The feeding means which comprises the reels 10 and 10 and the respective apertured discs 13 and 13 are such that, if the feeding means is utilized for the formation of quads of component conductors, then each of the quads has such twisting pitches that vary stepwise from one limited length to another throughout the entire length of the quad. The conductors 12 and 12 are then guided by guide rolls 15 and 15' and guide rolls l4 and 14', respectively, to an extruder machine 16. The extruder machine 16 has an extrusion head 17 and the conductors 12 and 12' respectively, are passed through dies 18,18 on the head 17. The construction and operation of the extruder machine 16 are well known per se and, as such, detailed description thereof is herein omitted. Since the plastic material covering the insulated conductors 19 and 19' initially is in a fused state, the insulated conductors l9 and 19' are passed through water in a cooling bath 20, whereby the plastic material is cooled and set. The insulated conductors 19 and 19' are drawn at a common and constant speed by capstans 21 and 21' over respective guide rolls 22 and 22' and a common guide roll 23. The

insulated conductors 19 and 19' are then wound in parallel to each other on a common reel 24. Designated by reference numeral 25 is a traversing guide pulley which reciprocates in the directions of the arrowheads so as to have the insulated conductors l9 and 19' wound uniformly on the reel 24.

As illustrated in FIG. 2, the secondary stage has five identical feedingvand twisting stations 26a, 26b, 26c, 26d, and 26e. are of the type disclosed in the applicants afore-mentioned prior U.S. patent application whereby the insulated component conductors are twisted at pitches varying stepwise from one limited length to another. The feeding and twisting stations 26a to 26 comprise respective feeding reels 24a to 242 which are not only identical with each other but identical with the winding reel 24 used in the primary stage shown in FIG. 1. The feeding reels 24a to 24c have mounted thereon coils 27a to 27c of insulated conductors 19 and 19.

The insulated conductors l9 and 19' which are wound in parallel with each other on each of the feeding reels 24a to 24c are unwound and drawn therefrom.

The pairs of the insulated conductors 19 and 19' are I passed through respective apertured discs 28a to 282v and are thereby twisted into respective strands 29a to 29s as the reels 24a to 24e are rotated relative to the respective apertured discs 28a to 28c.

The strands 29a to 296 are guided to capstans 30 and 30,. The strands 29a to 2912, drawn at a constant speed by the capstans 30 and 30', are passed through a strand retaining means 31 over to a common cable stranding station 32. Designated by reference numerals 33, 34, t

35 and 36 are guide rolls which may be provided to guide the strands 29a to 2% and adjust the'tension therein.

The cable stranding station 32 is herein shown as a rightand left-stranding apparatus which is a modification of the tensile helicoid high-speed stranding apparatus which is disclosed in the applicants U. S. Pat. No. 3,446,001. It comprises a rotary structure 37 which is rotatable about its axis, a traversing guide pulley 38 reciprocating in the axial direction of the rotary structure 32 as indicated by arrowheads, and a twisting disc 39 which is stationary're lative to the rotary structure 37. The strands 29a to 29e are thus fed to and wound on the rotary structure 37 and are twisted alternately in the right and left directions as they are unwound and passed into the twisting disc 39. The resultant cable 40 is then guided by guide pulleys 41 and 42 to an extruder machine 43 having an extrusion head 44 and is thereby covered with a protective tubular sheath. The cable 46 covered with the protective sheath is extruded through the die 45..

Because of the intrinsic construction and arrangement of each of the feeding and twisting stations 26a to 26e, each of the strands 29a to 2922' has twisting pitches which vary stepwise from one limited length to another throughout the entire length of the strand. It is, in this As an example, the experiments conducted by the inventor have revealed that, where a plastic extruder machine having a screw 65 mm diameter is used, a single 0.4 mm polyethylene insulated conductor is produced at the rate of about 1,200 meters per minute in the conventional practice'whilst, if the method according to the present invention is utilized, four similar conductors can be produced at the rate of about 650 meters per minute, which corresponds to about 2,600 meters perminute of a single conductor.

The arrangements which have described and illustrated in FIGS. 1 and 2 are merely preferred embodiments of the present invention and are not limitative of the scope of the invention. Various modifications and changes may be made without departing from the spirit and scope of the present invention.

In the primary stage of the arrangement according to the invention, for instance, a single insulated conductor may be fabricated, if desired. In this instance, it will be required that a larger-sized stranding apparatus having at least two feeding reels be used as the feeding means in the secondary stage. This is, however, not fully advisable in view of the enlarged dimensions of the production equipment and the increased productioncost.

instance, important that the adjacent two of the component strands eventually forming the stranded cable should have twisting pitches that differ from each other for providing satisfactory electrical properties of the resultant cable and preventing cross-talking, as is well known in the art. For this purpose, the feeding reels 24a to Me should be rotated at regulated speeds so that the strands 29a to 29 are formed at pitches different from one another at any given instant.

The feeding and twisting stations 26a to 26 make it possible to utilize feeding reels of increased dimensions, so that the strands 29a to 29e may be stranded into the cable 40 at the rate of about 50 to 70 meters per minute and the cable 46 covered with the protective sheath may be extruded for about ten hours without interruption.

The stranding station 32 of the tensile helicoid type permits operation for extended periods of time, adding to the performance efficiency for a significant reduction in production cost of the industrial communication cable.

It will now be appreciated from the foregoing description that the arrangement for manufacturing a communication cable in accordance with the present invention is advantageous for the simplification of the production process, reduction in the conveying cost and reduction in the floor space requirements, all of which will contribute significantly to an increase in the production rate of the insulators.

The feeding and twisting station which are used in the secondary stage as illustrated in FIG. 2 may be replaced with the known double-strandingmachine, if desired. Also, the rightand left-stranding apparatus of tensile helicoid type as shown in FIG. 2 may be replaced with a stranding machine of rotary drum type. In this instance, it is required that the step of covering the stranded cable with a protective sheath be separated from the cable stranding step.

Apart from this, it is well known that, where a quaded communication cable is manufactured, the insulated conductors are sometimes twisted around each other while being rotated so as to provide a satisfactory electrical balance of the final product. A similar effect will be attained if the feeding means in the primary stage is arranged to be of such type that, if the feeding means is used for the twisting of component conductors, then the resultant strand has the pitches of twisting which vary stepwise from one limited length to another. This is because of the fact that the conductor unwound from the feeding reel is subjected to a rotation when drawn from the extrusion die of the extruder machine so that, when a plurality of such insulated conductors are twisted into a strand in the secondary stage,

each of the insulated conductors is in a rotated state as it is. Such effect will also be attained if the feeding means of the above described type is used in combination with a winding reel of a relatively great drum diameter and a relatively small flange diameter. If, in this instance, the winding reel 24 (FIG. 1) or each of the feeding reels 24a to 24 (FlG. 2) has a drum of 330 mm outside diameter and flanges of 400 mm diameter, the conductor will be twisted one turn per travel of the conductor around the flange when the conductor is unwound from each of the feeding reels 24a to 242. This means that the conductor is twisted one turn per about 1,000 to 1,200 mm length when it is unwound from the feeding reel in the secondary stage, providing a satisfactory electrical balance of the finally produced communication cable.

hereinbefore.

According to one important aspect of the present invention, now, the production rate of the communication cable can be increased significantly with the conductor twisting step combined with the cable stranding step even though the rate of stranding is not very high.

According to another important aspect of the present invention, the entire construction of the feeding and twisting unit used for the production of strands of component conductors can be simplified without increasing the cost of production equipment.

According to still another important aspect of the present invention, the extrusion rate of the plastic insulated conductor can be increased considerably without major modification of the existing extruder'machine.

What is claimed is:

l. A method of forming a communication cable which comprises:

a. jointly winding a plurality of insulated conductors on each of a plurality of reels mounted forrotation about respective axes;

. thereafter rotating said reels about the respective axes at a first speed while jointly unwinding the conductors from each reel in a substantially axial direction at a second speed to a first twisting station associated with said reel;

0. continuously passing the conductors unwound from said reels at the respective first twisting stations in said direction through an apertured member rotating at a third speed substantially about the axis of the associated reel and thereby twisting the conductors unwound from each reel about each other to form a strand;

. continuously passing said strands through a second twisting station common to all conductors and twisting said strands, while passing through said second twisting station, to form a stranded cable;

e. continuously passing said cable through a covering station and covering the passing cable in said covering station with a protective sheath,

1. one of said first, second, and third speeds being held constant, and

2. one of the other two speeds beingvaried for varying the pitch of each strand stepwise from one section of said strand to another over the entire length of said strand.

2. A method as set forth in claim 1, wherein said insulated conductors are prepared by simultaneously passing a plurality of bare conductors continuously and at a common speed through an insulating station, and covering said bare conductors with respective layers of insulating material while passing through said station, the insulated conductors simultaneously produced being wound jointly on one of said reels at said common speed. Y

3. A method according to claim 2, wherein said insulated conductors are cooled after they are covered with said insulating material.

4. A method according to claim 2, wherein each of said. insulated conductors is twisted after it has been covered with said insulating material. 

1. A method of forming a communication cable which comprises: a. jointly winding a plurality of insulated conductors on each of a plurality of reels mounted for rotation about respective axes; b. thereafter rotating said reels about the respective axes at a first speed while jointly unwinding the conductors from each reel in a substantially axial direction at a second speed to a first twisting station associated with said reel; c. continuously passing the conductors unwound from said reels at the respective first twisting stations in said direction through an apertured member rotating at a third speed substantially about the axis of the associated reel and thereby twisting the conductors unwound from each reel about each other to form a strand; d. continuously passing said strands through a second twisting station common to all conductors and twisting said strands, while passing through said second twisting station, to form a stranded cable; e. continuously passing said cable through a covering station and covering the passing cable in said covering station with a protectIve sheath,
 1. one of said first, second, and third speeds being held constant, and
 2. one of the other two speeds being varied for varying the pitch of each strand stepwise from one section of said strand to another over the entire length of said strand.
 2. one of the other two speeds being varied for varying the pitch of each strand stepwise from one section of said strand to another over the entire length of said strand.
 2. A method as set forth in claim 1, wherein said insulated conductors are prepared by simultaneously passing a plurality of bare conductors continuously and at a common speed through an insulating station, and covering said bare conductors with respective layers of insulating material while passing through said station, the insulated conductors simultaneously produced being wound jointly on one of said reels at said common speed.
 3. A method according to claim 2, wherein said insulated conductors are cooled after they are covered with said insulating material.
 4. A method according to claim 2, wherein each of said insulated conductors is twisted after it has been covered with said insulating material. 